Direction finder loop



y 1 0- w. BERl QDT 2,201,807

DIRECTION FINDER LOOP Filed Dec. :1. 195a RAD/0 APPARATUS INVENTORWALTER BERN DT svjfgzwvw ATTORNEY Patented May 21, 1940 PATENT OFFICEDIRECTION FINDER LOOP Walter Berndt, Berlin, Germany, assigncr toTelefunken Gesellschaft fiir Drahtlose Telegraphic in. b. H., Berlin,Germany, a corporation of Germany Application December 31, 1936,.SerialNo. 118,458 In Germany November 9, 1935 7 Claims.

This invention relates to an improved direction finder loop or frameantenna for. transmitting and receiving radio frequency waves.

The present invention concerns a loop or frame antenna arrangement withno, or only very small antenna eifect.

As is known, the directional diagrams of frame antenna correspond to thecalculated ones only if the antenna effect of frame can be successfullyeliminated. Variousmeans are known in the art for accomplishing thispurpose. Frame and input circuit may be developed symmetrically; theframe or loop conductor may be screened electrically; the lead lines tothe frame may be grounded over differential condensers or the antennaefiect may finally be compensated by an auxiliary antenna. In spite ofall these measures, the antennaeffect still exists to a considerableextent and is always compensated by the means cited last, that is, by anauxiliary antenna. The antenna required must have a definite effectiveminimum height. But it is in many cases inconvenient to employ a large!auxiliary antenna. It is desirable for this reason to construct frameantennas with as small as possible antenna effect.

Therefore, in accordance with the invention,

a loop or frame is constructed in the manner that the leads to the frameor loop conductor ends pass through the perpendicular loop diameter todivide symmetrically the plane enclosed by frame. The lead line issuitably shielded metallically and the midpoint of the conductorconnected with the shielding member.

An exemplified embodiment is illustrated in the figure. R therein is aframe or loop conductor with one coil. A pair of loop leads Z aretwisted and connect at top points P1 and P2 of conductor R and areshielded by a metallic pipe S which passes through the diameter of theloop in the axis of rotation thereof and is connected with a mass or theearth. The midpoint of the frame coil or conductor R. is connected withthe shielding of the leads at a central point M.

A frame arrangement of this type has a very small antenna effect evenwhen the frame is disposed asymmetrically to the apparatus or earth.Measurements with a rotatable shortwave receiving frame resulted for theframe minimum in a receiver input potential of 1% of maximum while theusual frames showed about 10 to on the same wave range. At the sametime, both minima. of the arrangement according to invention are alwaysof equal sharpness, while in the frames used in the prior art thatsharpness is mostly different at the two sides.

A complete sharpening of the minimum may also be insured in thearrangement according to invention by means of auxiliary antenna. Inthat case, the auxiliary antenna-need is substantially smaller than inthe usual frames-due to the small antenna effect. Auxiliary antennas areusually sufficient whose limiting dimensions are considerably smallerthan the one of the frame.

A particular advantage or object of invention lies in the fact that thelength of the frame leads have no influence on the sharpness of theminimum.

The described principle may likewise be utilized for frames with severalcoils or conductor turns. The frame windings may further be electricallyscreened in known manner. The loop may have the form of a circle or apolygon; yet it may deviate therefrom, in particular the proportion:height to width. In rotatable frames it suits the purpose best toarrange the leads in axis of rotation. It is evident that allobservations made hold true for transmitter, as well as for receivernected to a point of the frame located opposite the earthing point.

What is claimed is:

1. In a directional antenna system to be used with radio frequency waveenergy having substantially no antenna effect, a rotatable loop aerialcomprising at least substantially one conducting turn with two openterminal ends, said loop being adapted to be energized by radiant waveenergy and positioned with its open terminal ends at the highestmechanical point on said loop to electrically maintain a point ofrelatively low radio frequency potential, a connection at a centralpoint on said conductor intermediate its terminal ends forming a pointof relatively low potential, leads connecting said terminals to highfrequency apparatus, and a metallic shield having its axis located inthe central plane of said loop and extending within the confines of theloop aerial for enclosing and electrically shielding said leads.

2. A directional antenna comprising a rotatable loop having at least oneconductor turn with two open terminal ends located at the extreme upperportion of said loop, a pair of leads each one of which is connected toone of the terminal ends of said rotatable loop, a metallic tubearranged to pass through the central portion of said loop and Within theconfines of said conductor turn, said pair of leads passing through saidmetallic tube to electrically divide said loop symmetrically withrespect to said conductor turn to reduce the antenna effect thereon, anda conductive connection from the midpoint of said conductor turn to saidmetallic tube.

3. A directional antenna comprising a rotatable conductive loop having aplurality of conductor turns with two open terminal ends located at theupper portion of said loop, a pair of conductive leads arranged to passsubstantially through the axis of rotation and within the confines ofsaid conductor turns, each one of said leads connected to one of theopen terminal ends of said conductor turns, and forming means forelectrically subdividing said loop symmetrically with respect to saidconductor turns to reduce the antenna effect on said loop.

4. A directional antenna comprising a rotatable circular loop having atleast one conductor turn with two open terminal ends located at theextreme upper portion of said rotatable loop, a pair of twistedconductive leads each one of which is connected to one of the terminalends and arranged to pass through the diameter of said loop, a metallicshielding pipe disposed within the diameter and axis of rotation of saidloop, said conductive leads passing through said shielding pipe toelectrically divide the conductor turn symmetrically to reduce theantenna eifect on said loop.

5. A directional antenna comprising a rotatable loop having at least onecircular conductor turn with two open terminal ends located at theextreme upper portion of said rotatable loop, a pair of conductive leadseach one of which is connected to one of the terminal ends of saidrotatable loop, a metallic shielding pipe disposed within the diameterof said conductor turn for shielding said leads, and a midpointconductive connection from the lower midpoint of said conductor turn andthe outside of said metallic shielding pipe, said midpoint conductiveconnection being connected to ground.

6. A directional antenna comprising a rotatable loop having a pluralityof circular conductor turns with two open terminal ends located at theextreme upper portion of said rotatable loop, a pair of conductive leadseach one of which is connected to one of the terminal ends of saidrotatable loop, a metallic shielding pipe located at the diameter ofsaid conductor turns for shielding said leads, and a midpoint conductiveconnection from the lower midpoint of said conductor turns and theoutside of said metallic shielding pipe, said midpoint conductiveconnection being connected to ground.

'7. A directive aerial comprising at least one turn of conductivematerial arranged substantially in a plane with the terminals of saidconductive material adjacent to each other to form a substantiallyclosed loop, means connecting a point on said conductor substantiallysymmetrically spaced from the terminals thereof to ground or equivalentpotential, leads connected to the terminals of said conductor passingacross said loop substantially in said plane, a shield member enclosingsaid leads substantially throughout their entire length across saidloop, and a connection between said shield member and said point ofcontact or equivalent potential.

WALTER BERNDT.

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